Existing studies at the cellular level with the Platinum coordination complex cis-dichlorobis (cyclopentylamine) Platinum II -DBCP - will be extended to the newer compound cis-dichlorobis (isopropylamine) trans-dihydroxy Platinum IV - DIP - which is highly water soluble and may have lower kidney toxicity than earlier compounds. Initially, the biological effects of DIP alone and in combinations with ionizing radiation will be established in vitro using Chinese hamster (ovary) cells in monolayer culture. These data will provide a base-line for the main objective, namely, the use of C3H mouse mammary tumour cells in monolayer and spheroidal cultures in vitro and as solid tumours in vivo to determine the biological effects of DIP and radiation and their interaction in various combinations. Monolayer cultures will be synchronised to determine age-responses and effects on progression through the cell cycle. Spheroidal cultures will complement these studies with respect to effects on the growth kinetics of a cell population in tissue form but under environmental control. Finally, responses of the solid tumours in vivo will be compared with those of intestinal epithelial cells, representing a normal cell population in the same animal which may limit drug and radiation dosage.